U.S. Pat. No. 4,962,218 discloses silicone-polyether copolymer surfactants for polyurethane foam manufacture, having polyether backbones with lateral and/or terminal siloxane pendants. Such materials are referred to as "inverted surfactants," because conventional silicone-polyether surfactants having siloxane backbones and polyether pendant groups. They were synthesized by hydrosilating a polyether bearing multiple olefinic pendants with a silicone precursor of the desired siloxane pendants, having the desired size and molecular weight. To prevent crosslinking reactions, this silicone intermediate had to be highly pure and could possess only one silanic hydrogen per molecule. Since normal, commercially relevant silicone production schemes involve an equilibration process, methods such as careful distillation of an equilibrated fluid (very labor intensive and inefficient) or non-equilibration routes such as those employed in U.S. Pat. No. 4,962,218 (also very labor intensive, using non-trivial techniques and air and moisture sensitive reactants) needed to be invoked to prepare the required monofunctional silicone Si-H fluid intermediates. As such syntheses of the required silicone intermediates involved non-trivial synthetic methods not currently commercially practiced, and/or required purification by laborious and expensive techniques, the resulting surfactants were commercially disadvantaged.
In addition, hydrosilations with certain types of silicone intermediates were inefficient, particularly the reaction employing the sterically bulky tris-(trimethylsiloxy)silane (hereinafter abbreviated M.sub.3 T' in accordance with accepted practice, M standing for Me.sub.3 SiO.sub.1/2 where Me represents a methyl group, and T' standing for HSiO.sub.3/2). Conversions of the polyether's olefinic pendants into silicone pendants were typically less than 45% for these reactions.
It is therefore desirable to have an improved synthetic route to these surfactants. Such a synthesis is the subject of the present application.
The first disclosure of polysiloxane polyoxyalkylene copolymers appears in U.S. Pat. No. 2,834,748 of Bailey, et al. These compositions were of the hydrolyzable type, having siloxane backbones and polyether pendant groups attached to the siloxane via Si-O-C linkages. Subsequently, the first disclosure of non-hydrolyzable polysiloxane polyoxyalkylene copolymers, in which the polyether pendants are attached to the siloxane backbone via C-O-C linkages, appears in U.S. Pat. No. 2,846,458 of Haluska.
The first application of polysiloxane polyoxyalkylene copolymers for the stabilization of urethane foam appeared in British Patent No. 892,136 of Hostettler. These copolymers were of the hydrolyzable type. The application of non-hydrolyzable copolymers to urethane foam stabilization soon followed.
In U.S. Pat. No. 3,573,334 of Wheeler, a vinyl siloxane cohydrolyzate was free radically grafted onto a nominally 2800 g/mole polyether (50% by weight oxyethylene and 50% by weight oxypropylene units). See Example II of the patent. The use of a vinyl siloxane cohydrolyzate rather than a pure mono(vinyl)siloxane ensured that true inverted copolymer structures would not be obtained. In fact, Wheeler did not disclose preparation of such a structure in this patent.
One example is known in which a polyether prepared by the coalkoxylation of propylene oxide and allylglycidylether (i.e. a PPO rubber) was grafted by a silane. See U.S. Pat. No. 3,305,943 to ESSO Research and Engineering. The resulting compositions are rubbers which would be unacceptable for the presently-contemplated end uses.
In the abstract of Japanese Patent 54/36397 to Kanegafuchi Chemical Industry Co., Ltd., it is disclosed that an alkoxysilane was grafted via hydrosilation to an allylglycidylether modified polyester (1,2-butylene oxide-phthalic anhydridepolyethylene glycol copolymer). These ether-ester block copolymeric compositions were used as coating and room temperature curable compositions.
U.S. Pat. No. 4,424,328 deals with modified methacrylate monomers useful in manufacture of polymers for contact lenses. It discloses addition of a hydrolyzable silane with one silanic hydrogen to a monomeric olefin-modified methacrylate, to yield a hydrolyzable silane-modified methacrylate which is next cohydrolyzed with silane monomers to yield a silicone-modified methacrylate monomer. Subsequent free-radical polymerization of this material yields a silicon-pendant PMMA plastic. This concept of polymerizing a silicone-modified monomer is inappropriate to prepare the inverted surfactants of interest in the present case since the necessary hydrolyzable silane-pendant epoxide monomer would undergo hydrolysis during the base-catalyzed alkoxylation reaction which produces the polyether.